Wānaka build cuts energy bill to just $1200
Building a small house was never going to be a compromise for one Wānaka couple – it was what they wanted anyway.
Sarah Allen, a Passive House consultant and business manager, and physiotherapist Tim Smith had lived in a small former council flat in London for five years.
Allen says they were pretty comfortable in their “maisonette apartment” and realised they didn’t need more space, which they would then have to heat. “We don’t have children, and 86m² is heaps big enough.”
But the real secret to the success of their new build lies in the design – there is no wasted hall space, for example, and adaptability has been built in. Rooms can have several uses, and sofas can become beds for guests.
The couple opted for a Passive House Low Energy Build, which was another priority. “We had visited a retrofitted Passive House open home in London. It was a 6-degree, cold, grey day in January, and we stepped into the house and were amazed how comfortable it was,” Allen says. “It was like this lightbulb moment when you realise what’s possible.
“Most people don’t know what it’s like to not have a house where condensation forms in the cold. You assume here that the Building Code will give you a comfortable dry home, but it often doesn’t, or if it does, it comes with big power bills.”
The couple’s power bill last year was a mere $1200, but Allen expects that this may increase to $1400 this year due to power company increases. “We are not home during the day, which helps keep that cost down.”
The house is heated by four wall-mounted panel heaters that are set to 17C when the house is empty, and 20C when they are home. A heat pump provides the hot water. “I think that makes a huge difference,” Allen says. “It’s in the garage, which is a slightly warmer space than outdoors.”
While the house is not a full certified Passive House, it does have Zehnder mechanical ventilation, 20cm-thick walls, triple glazing and extra-thick insulation. The concrete slab is heated from beneath with a timber floor directly fixed to the concrete, which also helps to ensure the heat doesn’t leak out in winter.
“You can’t put a price on the comfort,” Allen says.
“You don’t mind getting out of bed because the house is a comfortable temperature – the floor is close to the room temperature, and you don’t feel cold radiating off the windows.”
The couple did compromise a little by having a high raked ply ceiling in the living area, as they wanted a feeling of space to offset the home’s small footprint. For a similar reason, the sliding doors are 2.4m high, rather than the standard 2.2m. This also allows more natural light into the home.
In designing the house, the couple took a cue from universal design guidelines, which ensure ease of access. There’s a ramp along the rear of the house to provide access; doors are slightly wider than standard; and there is level access for the shower.
Allen says one of the most difficult aspects of the build was finding a section in the first place – most Wānaka sections come with covenants that dictate a minimum house size much larger than 86m².
And the cost? Allen says the cost was “a bit under $6000 per m²”, because even though it is a small house, the cost of the kitchen and two bathrooms are much the same as a larger house.
The house, which was designed by architect Virginia Barlow, has won an ADNZ Resene Kaitiakitanga Award. In announcing the award, the judges said: “A well-deserved National Award for this small house, that has gained the award for its excellent leadership in the low-energy field.
“While many houses may be looking at what Passive House design truly means, the Heights Whare is a great example of a client and a talented young designer working together with a common aim in mind.
“The result is a Passive House home that fits in perfectly to the surrounding suburban environment. Considered design, together with careful and thoughtful detailing, take this home to win on a national stage in both aesthetic results and in leadership, showing the way forward.”